1. Field of the Invention
The present invention relates to a vaporizer for generating a process gas from a liquid material, and a semiconductor processing system. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
A film formation process for forming a predetermined film on the surface of a semiconductor wafer is performed in manufacturing semiconductor devices. For example, a process of this kind is performed, using a low-pressure CVD (Chemical Vapor Deposition) apparatus. In low-pressure CVD apparatuses, a source material is supplied in a gaseous state to promote a chemical reaction, thereby depositing a thin film on the surface of a wafer. In apparatuses of this kind, there is a case where a process gas is generated by vaporizing a liquid material, and is supplied into a process chamber as a film formation gas.
Examples of a film formation process using a process gas generated by vaporizing a liquid material are as follows. Specifically, a process gas generated by vaporizing TEOS (tetraethoxysilane) and oxygen (O2) gas are used to form an SiO2 film. A process gas generated by vaporizing Si2Cl6 and ammonia (NH3) gas are used to form a silicon nitride (Si3N4) film.
Patent Document 1 (Jpn. Pat. Appln. KOKAI Publication No. 3-126872 (Page 3, Paragraph number 30, and FIG. 1)) discloses one type of a vaporizer for vaporizing a liquid material. According to this vaporizer, an atomized liquid material is supplied from a nebulizer into a vaporizing chamber heated at a predetermined temperature, and is vaporized there. However, this vaporizer cannot provide a sufficient heat exchange when the atomized liquid material flows through the vaporizing chamber. Consequently, the process gas obtained at the output pipe of the vaporizing chamber contains a lot of mist. Where the process gas is supplied into the reaction chamber of, e.g., a low-pressure CVD apparatus, the mist is deposited on the surface of a wafer and generates particles. Hence, the mist is a cause of particle generation on the wafer.
In light of the problem described above, the research group including the present inventors has developed a vaporizer 300 shown in FIG. 6. The vaporizer 300 includes a vaporizing chamber 302 provided with sidewall heaters 301 and a heat-exchange lower block 303 disposed inside the vaporizing chamber 302 on the bottom. The heat-exchange lower block 303 is also provided with, e.g., four rod-like heaters 304 embedded therein at intervals in an annular direction to vaporize a liquid material on the surface of the heat-exchange lower block 303. The heaters 301 and 304 are connected to a power supply section 310. An injector 305 is disposed at the top of the vaporizing chamber 302 and is configured to supply the liquid material in an atomized state into the vaporizing chamber 302. The liquid material is heated to, e.g., 150° C. and thereby vaporized by the sidewall heaters 301 of the vaporizing chamber 302 and the heaters 304 of the heat-exchange lower block 303. The liquid material thus vaporized is supplied as a process gas from the output port 306 to a consuming apparatus, such as a CVD apparatus.
However, the present inventors have found that this vaporizer entails a problem, as described later.